Detecting the presence of a moving object, such as a person, animal, or vehicle is important for many applications, including home or retail surveillance, security, marketing analysis, traffic analysis, people counting, vehicle counting, wild life tracking, etc. Video surveillance cameras, inductive loops, motion detectors, light curtains, etc. have typically been deployed to monitor for a moving object under a wide variety of settings such as access control points, retail environments, loading docks, driveways, backyards, and places of high security such as airports, train stations, nuclear facilities, army bases, naval bases, air force bases, etc. Each of these technologies have are limited in various aspects. For example, use of an inductance loop is often used to detect the presence of a vehicle at a stop light or at an entrance through a security barrier. However, installation of an inductance loop is typically complicated, requiring burying the inductance loop under a roadway. Further, it can be difficult to set the inductance loop to achieve the correct sensitivity—an insensitive inductance loop may result in a long wait for a vehicle operator, while an overly sensitive inductance loop may trigger false vehicle detections, and can result in unwanted or even dangerous actions responsive thereto. For example, a barrier gate arm at a security barrier may close on a car previously cleared to pass due to detection of a second car in a neighboring lane. Bicycles may be undesirably detected and a barrier gate arm may close on the bicyclist.
Systems other than an inductance loop may also be used to monitor a location. For example, a video camera may be used to detect loitering, left behind objects, count people, etc. Analysis of a single image or video obtained from one camera is useful in many applications, but incurs challenges in other applications. When attempting to detect the presence of a vehicle, ground shadows and spotlights formed by vehicle headlights may be processed as edges during video analysis, which may result in incorrect object detection.
Use of multiple video cameras can address inaccuracies in single camera video analytics, but multiple video camera systems are often computationally expensive. In addition, multi-camera video analytics often require precise and overly complex installation, mistakes in which can lead to poor results. Motion detectors are known to trigger false alarms in outdoor environments due to inclement weather conditions, moving tree branches, and the like. The motion detectors are typically oblivious to the types of objects detected. In another example, light curtains require precise alignment of LED transmitters and receivers. As such, the light curtains are not typically adopted for residential and commercial settings.